Homomorphic encryption is a form of encryption that allows computations to be carried out on ciphertext, thus generating an encrypted result which, when decrypted, matches the result of operations performed on the plaintext. Using symmetric homomorphic encryption, for instance, one computer could use its symmetric homomorphic-encryption key to encrypt two plaintext numbers, and then another computer could add the two encrypted numbers and send the result to the first computer which decrypts the result using its symmetric homomorphic-encryption key and thus has the sum of the two plaintext numbers. A variety of homomorphic encryption systems are known in the art.